Epoxy resins have been employed in coating compositions for many years. They have almost exclusively been applied in the form of powder coatings or organic solvent solutions. Because of environmental concerns, there has been a move to reduce the amount of organic solvents in those coatings applied by spraying, dipping, electrodeposition, rolling, flow coating, and the like.
One such attempt has been in the area of epoxy phosphate ester coatings as disclosed by Martin in U.S. Pat. No. 4,164,487, Campbell et al. in U.S. Pat. No. 4,397,970 and Ring et al. in U.S. Pat. No. 4,508,765. While the coatings offered by Martin, Campbell et al. and Ring et al. reduce or eliminate the use of organic solvents in liquid applied coating compositions by the use of water-borne coatings utilizing water miscible or water soluble epoxy compositions, the resultant coatings could stand an improvement in some of it properties such as blush after being subjected to steam pasteurization treatments and in formability as evidenced by reverse impact properties and in flexibility as evidenced by T-bend. The higher the reverse impact value of the coating, the better the formability characteristics of the coating. The lower the T-bend value of the coating, the better the flexibility characteristics of the coating.
It would therefore be desirable to have available, epoxy based liquid coatings which have: (a) reduced amounts of organic solvents, or (b) an improvement in one or more of its thermal or physical properties, particularly blush resistance, reverse impact and/or T-bend flexibility.